New transmission-line diagrams

IN THE DESIGN and operation of transmission lines the following quantities are of primary importance: sending-end power, receiving-end power, sending-end voltage, receiving-end voltage, power angle between sending-end and receiving-end voltage. Numerous diagrams have been developed for the solution of transmission-line problems, graphically illustrating relations between some of the afore-mentioned quantities. Among these, the modified Evans and Sels charts, based on the general circuit constants ABCD, have found wide acceptance.^1,2,3 In these charts the determination of the power at one end with the power given at the other end requires a transfer of points from one chart to another. It is one of the purposes of this paper to supplement the modified Evans and Sels diagrams in such a manner that this transfer of points can be eliminated. This can be accomplished by relating power at one end to power at the other end directly, without intermediate quantities such as voltage ratio and power angle. The diagrams developed are essentially admittance-circle diagrams, relating admittance at one end to admittance at the other end.